Conjugate heat transfer (CHT) stands for heat transfer between solids and fluids.

We developed a numerical model for convective cooling of electrical devices using Elmer FEM, OpenFOAM and EOF-Library software packages.

In the context of EOF-Library, the electromagnetic analysis is be done using Elmer FEM software, while turbulent flows and heat dissipation are solved using OpenFOAM. Nowadays it is common to study electromagnetics independently from fluid dynamics, which reduces problem complexity, but is less accurate comparing to fully coupled multiphysics problem. There is demand for more accurate models which follows from the need for smaller, lighter, energy-efficient and more reliable electrical devices.

Air flow through electric heater

Reduced model for domestic heater. Constant electric current is passing through coils that have temperature-dependent conductivity. Most of the current flows the shortest path therefore higher current and dissipated heat densities are located on the inner parts of curved surfaces.

Convective cooling of electrical motor

Efficiency of electrical motors used in car industry nowadays is above 90% and can reach astonishing 97% (e.g Tesla Model 3). All energy that is not turned into useful work, like turning the rotor, is wasted as heat that needs to be removed. Accumulation of heat leads to high temperatures that, consequently, can decrease motor efficiency due to increased electrical resistance of copper windings. In more serious cases overheating will cause demagnetization of permanent magnets and breakup of dielectric materials (epoxy, plastics etc.).

Electrical components of motors require numerical solvers for electromagnetic fields and are typically modelled using the finite element method (FEM), while turbulent flows and conjugate heat transfer (CHT) are solved using the finite volume method (FVM). In industry these problems are computed as independent physics processes. This saves simulation time and reduces the complexity of the problem, but also is less accurate compared to the coupled multiphysics problem. The need for smaller, lighter and more energy efficient electrical devices makes cooling more challenging; therefore, more accurate models are needed.

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